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https://issues.apache.org/jira/browse/CALCITE-1488?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15657351#comment-15657351
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Julian Hyde edited comment on CALCITE-1488 at 11/11/16 4:32 PM:
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Thanks [~julianhyde]! I applied this patch locally and it works for me.
I still have a problem with Aggregates that lack a group set, like {{SELECT
COUNT\(\*) FROM s.foo WHERE 1 = 0}}. PruneEmptyRules doesn't reduce that, since
the result is going to be one row, not empty. The ValuesReduceRules don't
either, because they don't touch Aggregates.
I ended up addressing this with a rule on my end:
https://gist.github.com/gianm/1c192a47a7ce284be8af986f97e6dd8f
Does that approach make sense? If so do you think it makes sense to contribute
to Calcite?
One thing I'm not sure about is if there's a better way to figure out what
should be 0 and what should be NULL other than hard-coding COUNT and SUM0.
was (Author: gian):
Thanks [~julianhyde]! I applied this patch locally and it works for me.
I still have a problem with Aggregates that lack a group set, like {{SELECT
COUNT(*) FROM s.foo WHERE 1 = 0}}. PruneEmptyRules doesn't reduce that, since
the result is going to be one row, not empty. The ValuesReduceRules don't
either, because they don't touch Aggregates.
I ended up addressing this with a rule on my end:
https://gist.github.com/gianm/1c192a47a7ce284be8af986f97e6dd8f
Does that approach make sense? If so do you think it makes sense to contribute
to Calcite?
One thing I'm not sure about is if there's a better way to figure out what
should be 0 and what should be NULL other than hard-coding COUNT and SUM0.
> ValuesReduceRule should ignore empty Values
> -------------------------------------------
>
> Key: CALCITE-1488
> URL: https://issues.apache.org/jira/browse/CALCITE-1488
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.10.0
> Reporter: Gian Merlino
> Assignee: Julian Hyde
> Fix For: 1.11.0
>
>
> ValuesReduceRule doesn't propagate rowType on Project of empty Values. If
> ValuesReduceRule is trying to reduce a Project on top of an empty Values,
> then changeCount ends up 0, and it returns the underlying Values. This leads
> to an assertion failure because the returned Values does not have the
> expected rowType.
> One way to fix this is changing the "Filter had no effect" logic from
> "{{changeCount == 0}}" to "{{changeCount == 0 && projectExprs == null}}".
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